Unfortunately, Moalem didn't have much time to flesh out his ideas, because Stewart, mindful of the audience, kept jumping around.
I noticed that Moalem wore a yarmulke during the interview, and wondered if he worked at my hospital. Indeed, he does. The very next day, a publishing agent contacted me, offering to send a copy of Moalem's book if I'd review it online . I agreed, and made a mental note to finish the last two books that were sent to me under similar arrangements (yes, blogging's been good to me, Howard).
But Survival of the Sickest had something going for it that those other books did not -- a long bus trip in which I could sit and read the thing. And it's a quick read, chock full of tidbits and groan-inducing puns.
Others have pointed out similarities to last year's cocktail-party companion, Freakonomics. Levitt and Dubner's book was about how clever approaches to problems can yield surprising answers. There was no overarching hypothesis. Sickest is a little more organized -- but not much more.
Moalem uses a few big examples to support the idea that some long-term diseases can provide short-term benefit -- hemochromatosis as a way or warding off bacterial infection, diabetes as a defense against frostbite, and thalassemia, sickled cells, and G6PD deficiency as protection from malaria. All these subjects are treated airily, with a smattering of supporting evidence, and no real consideration of criticism.
That's ok. This book isn't really about proving a hypothesis. In fact, it truly shines in its asides and extraneous information. One chapter, "The Cholesterol Also Rises," tries to build the case that Africans experience high cholesterol (and its associated risks) because that's nature's compensation for developing darker skin. Darker skin means it's harder for the body to make Vitamin D, but extra cholesterol building blocks would help the process along.
What makes the chapter really memorable, though, are little tidbits about race, skin color, how light can trigger sneezes, and the explanation for the Asian flush when drinking alcohol. One aside featured the pituitary gland, which ultimately triggers the melanocytes that tan the skin. The pituitary responds to the optic nerve's sensation of light -- so tanning with sunglasses is actually less effective than keeping your eyes wide open to the sun.
I love that stuff, and dog-ear pages with factoids that I'll want to recall. Sickest had over two dozen dog-ears by the end, which is right up there with Freakonomics and Gladwell's books.
It was enough to make me overlook the really tenous evidence Moalem uses to support his most contentious theory -- that diabetes' prevelance is an adaptation to the last ice age. Sure, it's more common in among Northern Europeans. And sure, some frogs use hyperglycemia as an antifreeze during hibernation season.
But he also invokes the fact that rats become insulin-resistant in the cold, and that human fibrinogen levels rise in winter (which he also links to our higher rate of MI and stroke). These may not be so much cold responses as a simple molecular kinetics -- a lot of biochemical reactions don't work as well in cold temeperatures. Besides, he says high fibrinogen in winter is evolution's way of protectiong against ice-crystal damage, but he fails to note that clotting is impaired by hypothermia -- clotting factor levels are not correleted with activity.
Moalem cites the fact that type I diabetes is most often diagnosed in the autumn, when "temperatures start to fall." Well, I've heard this tidbit before, but it was used to support the viral theory of type I diabetes -- and frankly, that theory has a lot more support. Moalem doesn't mention it.
The book's final chapters don't even try to support his idea that chronic disease may help in the short term. The chapters just funnel Moalem's extensive knowledge of evolutionary biology trivia to the reader. And it's entertaining. I'd heard some stuff on the blogosphere about toxoplasmosis influencing rat behavior, and potentially human behavior, too -- but Moalem is able to expand upon it and put it in context. Also, he includes a nice section on the Aquatic Ape hypothesis, which I plan to share with my friend's wife before she gives birth in a spa this summer.
So, this book certainly gave me some things to think about and file away. But in an anecdote that's fairly typical, Moalem notes that in times of societal stress (such as former East Germany in 1990 and the US in the fall of 2001) women are more likely to miscarry -- but only the male fetuses. Interesting, isn't it? Is it because males are more demanding on resources? Or because in a crisis, it's better to have more females around to ensure survival?
It turns out no one knows. It's not even clear how it's happening. Evolutionary biology can give us some possible explanations, all of which can be satisfying from a teleologic perspective. But unfortunately, none of them may be the right answer. None of them may advance our understanding or treatment of disease. Still, it makes for great conversation.